The Russian revolution happened in 1917. The radical communist group called the Bolsheviks overthrew their tsar. The ideas of communism are very different from democracy, so the United States saw the war as a way to prevent any other countries from succumbing to communism.
The February Revolution of 1917 ;
The Russian Revolution of February 1917 led to the abdication of Tsar Nicholas II and the establishment of a Provisional Government in Russia. This change allowed President Wilson to frame the U.S. entry into World War I as a defense of democracy against authoritarianism, contributing to the decision to declare war on Germany. Wilson's request for war was influenced by both the change in Russian governance and aggressive actions by Germany, such as unrestricted submarine warfare.
;